U.S. Pat. No. 5,702,350 to Vry et al. describes a system in which an adapter is used to connect a stereoscopic endoscope to stereoscopic electronic documentation devices (e.g., stereoscopic CCD cameras). This system utilizes a stereoscopic endoscope (or line of stereoscopic endoscopes) specifically designed as a part of the overall stereoscopic system described in the patent. As shown in the patent, the stereoscopic endoscopes have specially designed optics and specially designed mechanical connectors to match with the set of stereoscopic documentation devices (e.g., stereoscopic CCD cameras).
As opposed to the cited prior art, and as will hereinafter be discussed in detail, the present invention teaches a method and apparatus for adapting virtually any conventional, commercially-available non-stereoscopic endoscope (i.e., a 2D endoscope) to a fixed stereo camera so as to obtain stereoscopic 3D visualization.
More particularly, the configuration of a typical conventional rigid non-stereoscopic endoscope is well known in the art. FIG. 1 shows the structure of the endoscope. The non-stereoscopic (i.e., 2D) endoscope 10 comprises an elongated shaft 11, a proximal housing 12, a light post 13 and an eyepiece 14. The shaft 11 typically includes at least one thin-wall inner tube 15 in addition to the outer tube 16. Illumination fiber bundle 17 extends from the light post 13 to the distal end of the endoscope and typically is sandwiched between the inner tube 15 and the outer tube 16. The inner tube 15 carries the optical train that typically comprises an objective lens 18, and a number of rod-lens optical relay systems 19a, 19b, . . . , 19n. Some endoscopes feature an oblique direction of view (e.g., 30° with respect to the longitudinal axis of the shaft 11), typically achieved by a prism 20. A negative lens 21 is disposed at the distal tip of the endoscope for expansion of the optical field of view and is hermetically sealed to the shaft 11. Sometimes an additional plane window is used at the distal tip of the endoscope for sealing the assembly, instead of using the negative lens 21 for both optical and sealing purposes. The objective lens 18 creates the first intermediate image 22 of an object under observation. Each relay system 19 creates a next intermediate image, thereby carrying the image of the object through the narrow shaft from the distal end of the endoscope 10 to the proximal end of the endoscope 10. The last intermediate image is created at the proximal end of the endoscope 10.
FIG. 2 shows the detail of a typical proximal end construction of the 2D endoscope 10. The last optical intermediate image 22n is created behind the last optical relay system 19n. At the location of the image 22n, a field stop 23 is disposed that delineates the designed optical field of view and removes stray light. Typically, the field stop 23 is constructed as a thin diaphragm with a round opening in its center. An ocular lens 24 is disposed proximal to the field stop 23 at such a distance that the field stop 23 locates in the vicinity of the first focal plane of the ocular lens 24. On account of this construction, the ocular lens 24 creates a virtual magnified image of the field stop 23 and of the intermediate image 22n at a long distance (typically from 250 mm to infinity) from the ocular lens 24. This image may be observed by direct viewing through the eyepiece 14. The optical beam emerging from the ocular lens 24 may be considered collimated. A window 25 is disposed proximal to the ocular lens 24 and is hermetically sealed to the proximal housing 12. Thus, the 2D endoscope 10 represents a single hermetically sealed sterilizable assembly that may not be disassembled by the user. The eyepiece 14 is affixed to the proximal housing 12 and is typically made out of chemically resistant plastic, e.g., PEEK. Typically the shape and dimensions of the eyepiece are in compliance with the German standard DIN 58105. FIG. 3 shows the DIN 58105 specifications.
It is well known in the art that eyepieces formed in compliance with DIN 58105 have become the industry standard, and all major manufacturers of endoscopes produce products compatible with this eyepiece standard. When the endoscopes are used in conjunction with endoscopic cameras, the common shape of the eyepieces from different manufacturers (i.e., all complying with the DIN 58105 standard) allows for connection of different endoscopes to different cameras all across the industry. In other words, eyepieces complying with the DIN 58105 standard have become an industry standard interface for commercially available 2D endoscopes. The eyepiece is typically releasably attached to the endoscopic camera head with a locking mechanism that allows for rotation of the endoscope around its mechanical axis. Conventional endoscopes per the above description constitute the majority of commercially available endoscopes and may be found in various catalogs of endoscope manufacturers. Just a few examples are given below:
(1) Laparoscope 5 mm×30°, Part Number 26046BA by Karl Storz;
(2) Laparoscope 10 mm×0°, Part Number A4801A by Olympus;
(3) Bariatric Laparoscope 10 mm×30°, Part Number 502-657-030 by Stryker;
(4) ENT Scope, 4 mm×30°, Part Number T4302 by Linvatec; and
(5) Laparoscope 10 mm×30°, Part Number 7207945 by Smith & Nephew.
Typically the endoscope is coupled to the camera via an optical device, i.e., an adapter, also known as an endocoupler or a camera coupler. The function of this optical device (i.e., adapter) is to focus the collimated light beam coming out of the ocular lens 24 onto the image sensor of the camera. Endocouplers include focusing optics and means for focus adjustment (most often via a manually rotatable focus ring). Typically manufacturers offer a range of endocouplers having different focal lengths. The image size obtained for a given endoscope on a given image sensor will be proportional to the focal length of the endocoupler. Some manufacturers produce endocouplers with optical zoom capability. The endocoupler may represent a stand-alone, hermetically-sealed, sterilizable device whose proximal end is releasably attached to the camera head and whose distal end releasably couples to the DIN 58105 eyepiece of the endoscope, thereby allowing the endoscope to rotate. Alternatively, the endocoupler may be permanently attached to the camera head (becoming an integral part of the camera head), in which case the distal portion of the integrated camera head (i.e., the camera head plus the endocoupler) will have a releasable locking mechanism for the DIN 58105 eyepiece.
Examples of just a few of the commercial stand-alone endocouplers are given below:
(1) Endocoupler, 30 mm focal length, Part Number 7204823 by Smith & Nephew;
(2) Endocoupler, Part Number PV127S by Aesculap;
(3) Zoom endocoupler, Part Number PV126S by Aesculap; and
(4) Parfocal Zoom Coupler, (20-37 mm) by Solos Endoscopy.
Examples of a few of the commercial endocouplers which are integrated with camera heads include:
(1) Camera head with coupler, Part Number OTV-SP1H-NA-12E by Olympus; and
(2) TRICAM® Parfocal Zoom 3-Chip Camera Head, Part Number 20221030 by Karl Storz.